Hull secure bragging rights
Three tries in seven second-half minutes proved crucial as Challenge Cup finalists Hull leapfrogged bitter rivals Hull KR in the Super League table.
A penalty try for Kirk Yeaman and further touchdowns from Jamie Shaul and Joe Arundel helped the visitors turn the match around and emerge triumphant in the derby at MS3 Craven Park.
It was Hull's third successive win and a third straight defeat for the Robins.
Gareth Hock grabbed four touchdowns for Widnes who tossed away victory by conceding three late tries to Castleford, going down 42-38.
The Vikings were behind 24-8 before fighting back to lead 34-24 until 12 minutes from time.
Then Cas stunned Widnes with Adam Milner, Weller Hauraki and Michael Channing crossing for tries converted by Kirk Dixon.
The win moves Cas level on points with Widnes after a 16-try thriller.
Thomas Bosc's last-gasp drop-goal sealed a vital 23-22 win for Catalan Dragons over Bradford in the race for the play-offs.
On a day when all the pre-match headlines centred around Elliott Whitehead's return to Odsal after his acrimonious departure earlier this year, it was the boot of Bosc that snatched the victory for the Dragons in a game they looked well out of at half-time, trailing 18-4.
Keith Lulia went over twice for the Bulls but it was not enough as tries from Mathias Pala, Jamal Fakir, Brent Webb and Ian Henderson handed the French visitors the win.
